Backward tracking and quantitative analysis of water vapor transport at different altitudes during rainstorms on the eastern, western, and east-west foot of Helan Mountains from 2001 to 2019 were conducted using the HYSPLIT trajectory model, based on hourly precipitation observations and GDAS reanalysis data with a spatial resolution of 1.0°×1.0° and a temporal resolution of 6 hours. It was found that significant differences exist in water vapor transport patterns at different altitudes during rainstorms across different regions of Helan Mountains. At the eastern foot, the southerly path was identified as the primary transport route below 3000 m, with a water vapor contribution rate of 57.3% to 75.2%. The contribution of the westerly path was observed to increase with altitude, reaching 100% at 5000 m. At the western foot, the westerly path was found to be the dominant transport route, with a water vapor contribution rate ranging from 31.8% to 67.5%. The southerly path was observed to be secondary, with contributions ranging from 23.8% to 68.2%, while the northerly path appeared only at 100 m and 1000 m, contributing 28.9% to 39.4%. In the east-west foot region, the westerly path was determined to contribute 100% of the water vapor at all altitudes. The Eurasian westerlies were identified as the predominant source of water vapor, particularly during rainstorms in the east-west foot region, where the water vapor contribution was the highest at all altitudes except at 1000 m. Secondary water vapor sources included the Qinghai and Gansu regions, the Middle-Lower Yangtze Plains, and the waters of the Black Sea, Caspian Sea, Lake Balkhash, and Lake Baikal, which were found to supply moisture to rainstorms at the east-west, eastern, and western feet, respectively. The Hengduan Mountains were identified as contributing moisture at isolated altitudes during rainstorms at the eastern and western feet, though its contribution was minimal.